1. Field of the Invention
The present invention relates to an electromagnetic relay that switches between conducting and interrupting currents flowing through the electromagnetic relay, the currents being two types of currents of which magnitudes are different from each other and which flow through mutually opposite paths which are via the electromagnetic relay.
2. Description of the Related Art
Conventionally, an electromagnetic relay is known that is used as a relay in a driving circuit in an electric vehicle, a hybrid vehicle, and the like. The electromagnetic relay is used to switch between conducting and interrupting a current.
As shown in FIG. 1 and FIG. 2, an electromagnetic relay 9 includes a pair of contact sections 93. Each contact section 93 is configured by a movable contact 931 and a fixed contact 932. The contact section 93 is opened and closed by a magnetic force from a coil (not shown). The pair of fixed contacts 932 are held by a fixed holder 934. The pair of movable contacts 931 are held by a movable holder 933 such as to mutually short-circuit. The contact sections 93 are opened and closed by the movable holder 933 moving toward and away from the fixed holder 934 by the magnetic force from the coil.
In the electromagnetic relay 9, when the coil is energized, the contact sections 93 are closed by the magnetic force generated by the coil, creating a conductive state. When the coil is de-energized, the magnetic flux of the coil disappears. The contact sections 93 are opened, creating an interrupted state.
During transition from the conductive state to the interrupted state, an arc 8 may be generated in the contact section 93, as shown in FIG. 2. Arc-extinguishing magnet members 94 are disposed in the electromagnetic relay 9 to extinguish the arc 8, as shown in FIG. 1. Each arc-extinguishing magnet member 94 is disposed adjacent to the outer side of each contact section 93 (refer to, for example, Japanese Patent Laid-open Publication No. 2008-226547).
As a result of a magnetic field being generated by the arc-extinguishing magnet member 94 in the space in which the arc 8 is generated, Lorentz force F acts on the arc 8, thereby extending the arc 8. As a result, the arc 8 can be extinguished while preventing increase in the distance between the contacts in the contact section 93. In FIG. 2, reference number 8a indicates the arc 8 in a state prior to being extended. Reference number 8b indicates the arc 8 in the extended state. The same applies to FIG. 3, described hereafter.
However, when the arc 8 is extended by the Lorentz force F as described above, both end points 83 and 84 of the arc 8 may move from the fixed contact 932 and the movable contact 931 to the fixed holder 934 and the movable holder 933. Here, as shown in FIG. 1, the length direction of the movable holder 933 is perpendicular to the direction in which the arc 8 is extended. The length direction of the fixed holder 934 is roughly parallel with the direction in which the arc 8 is extended. Therefore, as shown in FIG. 3, when the direction in which the arc 8 is extended and the extending direction of the fixed holder 934 match, one end point 83 of the arc 8 moves along the fixed holder 934, making extension of the arc 8 difficult. Therefore, when the direction in which the arc 8 is extended and the extending direction of the fixed holder 934 match, the arc 8 cannot be sufficiently extended. Arc-extinction may become difficult to perform.
Therefore, a design is considered in which the direction in which the arc 8 is extended and the extending direction of the fixed holder 934 are opposite directions to each other.
However, when the electromagnetic relay 9 is used as a relay in a driving circuit in an electric vehicle, a hybrid vehicle, and the like, the directions of the current flow through the electromagnetic relay 9 during power running and during regeneration are opposite. Therefore, the directions in which the arc 8 is extended when the current is interrupted during power running and when the current is interrupted during regeneration are opposite. In either one of the instances, the direction in which the arc 8 is extended matches the extending direction of the fixed holder 934. In FIG. 1, solid-line arrows indicate the arc 8 generated when the current is interrupted during power running. Broken-line arrows indicate the arc 8 generated when the current is interrupted during regeneration.
In this way, at each of the two contact sections 93, the direction in which the arc 8 is extended and the extending direction of the fixed holder 934 cannot to be set to be opposite to each other when any one of the currents flowing in the two mutually-opposite directions is interrupted.